(View looking South over Salt Pond, from the Cape Cod National Seashore Visitor center)

Monitoring Nutrients in Ground Water with Robowell at Salt Pond Eastham, Massachusetts

at the Cape Cod National Seashore in cooperation with the National Park Service

A Robowell prototypes have been put in place near the Cape Cod National Seashore to monitor ground-water quality upgradient and downgradient of the National Seashore Visitor's Center septic leach field as part of the The National Park Service - U.S. Geological Survey Water Quality Partnership Program. This research project is designed to assess the suitability of the technology for monitoring nutrient transport in ground-water to saltwater bays and estuaries.

Photographs showing the Robowell installation and the enclosed equipment at the Cape Cod national Seashore.

Problem Statement:

Ground-water is recognized as a potential source of nutrients and other contaminants that affect the ecological health and eutrophication status of estuaries and coastal fresh-water bodies (U.S. Environmental Protection Agency, 2001). A number of studies indicate that the concentrations of ground-water contaminants increase with increasing housing density (Morrill and Toler, 1973; Quadri, 1984; Persky, 1986). The rapidly increasing population of the U.S. coastal zone, therefore, may exacerbate ground water contamination and thereby degrade the ecological health of coastal waters. Some of the fastest growing U.S. coastal areas are on the Atlantic coast, where the National Park Service has major stewardship responsibilities. On Cape Cod, for example, the year-round population has doubled since 1970, and increased five-fold since 1940 (Cape Cod Commission, 1996). Residential septic systems have been shown to be a major source of ground-water contamination and nutrient loading to the region’s fresh and salt-water resources (Weiskel and Howes, 1991, 1992; Portnoy and others, 1998; Nowicki and others 1999) in the Cape Cod region. More recently, studies have identified wastewater as the source of a large number of organic compounds, which may cause endocrine disruption, cancer, and other adverse ecological effects (Koplin and others, 2002). Early detection and source control (before contaminant plumes affect the surface water ecology) is important because nutrient recycling in aquatic systems can accelerate the pace of eutrophication once a nutrient plume arrives. For example, rooted macrophytes recycle nutrients from algae and macrophytes that have died, settled to the bottom, and have been incorporated into bottom sediments (Cooke and others, 1993). Therefore, long-term ground-water monitoring efforts may be necessary to quantify short-term variations and long-term trends in ground-water quality and flow. This information can be used to predict the potential effect of changes in ground-water quality before the effect of eutrophication is noted in coastal ponds and estuaries when the plume of contaminants discharges to the coastal zone.

Manual sampling is a necessary component of ground water quality monitoring efforts, but it has technical and financial limitations. Most of the costs involved in operating ground-water monitoring networks are for the labor and materials required for manual water-sample collection (Zhou, 1996). Minimizing the cost of ground water monitoring programs by using statistical strategies to reduce sampling frequency may result in data that are inadequate to (1) determine representative mean (or median) values of water quality properties and constituents; (2) detect long-term trends, periodic fluctuations, and abrupt changes in water quality; and (3) identify the accuracy of the resulting estimates of the trends (Johnson et al. 1996; Zhou 1996). Use of automated ground water monitoring stations can be used to optimize manual sampling efforts because these stations provide information necessary to characterize the periodic samples within a real-time record.

It has been noted that electronic instruments are ideally suited to gathering information regarding transient events and that automated water-quality monitoring systems offer an opportunity to study events on fine time scales, which cannot be sampled using other means (Granato and Smith, 1999a; b; 2001). Historically, however, investigators have lowered monitoring instruments into the screened zone of a well to passively measure water-quality properties in the well under the assumption that these measurements were representative of the quality of water in the surrounding aquifer. Research and experience, however, show that passive monitoring commonly does not provide representative measurements of water quality in the aquifer surrounding a monitoring well, and pumping well water is necessary to ensure representative measurements (Church P.E., and Granato, G.E., 1996; Reilly and LeBlanc, 1998; Smith and Granato 1998, Granato and Smith, 1999a; b; 2001; Craig Wiegand, Water Superintendent, Provincetown Water Department written commun., 2001).

Robowell is an automated ground-water monitoring system that provides real-time data without incurring the high labor and laboratory costs associated with manual sampling. The Robowell system can monitor ground-water quality and water level in one or more wells at a monitoring site using proven sampling methods (Granato and Smith, 1999a; b; 2001). This technology, if used with periodic manual sampling and appropriate calibration, provides the information necessary to detect abrupt changes, short-term variability, and seasonal and long-term trends in water quality and water levels. When Robowell detects these changes, it can quickly alert an operator. These capabilities make Robowell a steadfast sentry that can detect and report changes in water-quality or flow direction at contaminated sites, near potential sources of contaminants, or near discharge zones at critical coastal estuaries and fresh-water bodies.

An automated ground-water monitoring demonstration project is ideally suited for the Cape Cod National Seashore for a number of reasons. First, the NPS has selected the National Seashore as the prototype-monitoring park for the Atlantic and Gulf Coast biogeographic region (Roman and Barrett, 1999). Protocols developed at the Cape Cod National Seashore will be used widely in the long-term ecosystem-monitoring program of the NPS. The USGS Water and Biological Resources Disciplines are currently testing and compiling methods for use by the NPS, and a Robowell monitoring study will develop a protocol that can be used in this and other NPS management sites. Second, the Cape Cod National Seashore has a number of recognized management issues (Godfrey and others, 1999) including (a) population growth in communities immediately upgradient of coastal water bodies; (b) long-term histories (over 350 years) of waste disposal practices that may affect ground-water quality; and (c) an unusually large number of private residences (600) within the management area that represent continuing sources of septic wastewaters and other contaminants. Third, an automated ground-water monitoring study in the Cape Cod National Seashore management area would benefit from an unusually good understanding of the Region’s hydrogeology (Masterson and Barlow, 1997; Barlow, 1997) and could potentially be used augment ongoing water-resources studies on Cape Cod (for example, Portnoy and Soukup 1990). Furthermore, work at this site would provide further opportunities for collaboration among the USGS Geologic, Water Resources, and Biological Resources Disciplines, and CACO natural resource staff, all of whom are conducting related studies of the Seashore’s geologic framework, hydrology, and aquatic ecology. Finally, using Robowell, a technology developed and patented by the USGS at a high profile site such as the Cape Cod National Seashore Visitor’s Center would provide an opportunity for outreach and technical transfer, which would be a showcase for advanced technical developments made by the Department of Interior within our mission to be good stewards of the Nation’s resources.
 

Progress:

This project began with an intensive drilling and sampling program (including over 30 well-screen locations) to determine the location and depth of the septic plume from the CACO visitor's center.  Once the centroid of the current plume was estimated Robowells were installed upgradient and downgradient of the septic system. Ground-water was sampled for physical properties, major ions, and nutrients. The Robowell systems have been measuring ground-water levels since March 2004 and have been measuring real-time ground-water quality since May 2004.  Robowell measurements and manual-sampling results indicate that nutrients and total dissolved solids are still elevated over background concentrations even though the old septic system was decommissioned in 2002.

Real-Time Data:

Up-gradient ground-water levels, air temperature, and humidity

Links:

Cape Cod National Seashore (CACO)

Other Environmental Studies at CACO

The National Park Service - U.S. Geological Survey Water Quality Partnership Program
 

References:

Barlow, P.M., 1997, Particle-tracking analysis of contributing areas of public-supply wells in simple and complex flow systems, Cape Cod, Massachusetts: U. S. Geol. Survey Water-Supply Paper 2434, 66 p.

Cape Cod Commission, 1996, Cape Trends: Demographic and economic characteristics and trends, Barnstable County, Cape Cod, 3^rd ed.: Cape Cod Commission, Barnstable, Mass. 122 p.

Church P.E., and Granato, G.E., 1996, Bias in ground-water data caused by well-bore flow in long-screen wells: Ground Water, v . 34, no. 2, p. 262-273.

Cooke, G.D., Welch E.B., Peterson S.A., and Newroth, P.R., 1993, Restoration and management of lakes and Reservoirs 2^nd ed., Boca Raton, Florida, Lewis Publishers, 548 p.

Granato, G.E., and Smith, K.P., 2001, Automated groundwater monitoring system and method: Washington D.C., U.S. Government Patent and Trademark Office, United States Patent 6,021,664, 31 p.

Granato G.E., and Smith, K.P., 1999a, Robowell: An automated process for monitoring ground water quality using established sampling protocols. Ground Water Monitoring and Remediation, v. 19, no. 4, p. 81-89. Available on-line at URL http://ma.water.usgs.gov/automon/

Granato, G.E., and Smith, K.P., 1999b, Robowell--A reliable and accurate automated data-collection process applied to reactive-wall monitoring at the Massachusetts Military Reservation, Cape Cod, Massachusetts, in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Charleston, South Carolina, March 8-12, 1999--Volume 3 of 3--Subsurface Contamination from Point Sources: U.S. Geological Survey Water-Resources Investigations Report 99-4018C, p. 447-456. Available on-line at URL http://ma.water.usgs.gov/automon/ 

Granato, G.E., and Smith, K.P., 2001, Automated groundwater monitoring with Robowell--case studies and potential applications:  in Jensen, J.O., and Burggraf, L.W., (eds.) Chemical and biological early warning monitoring for water, food, and ground proceedings 4574: Bellingham WA, Society of Photo-optical Instrumentation Engineers, Photonics Boston, 28 October 2001, p 32-41.  Available on-line at URL http://ma.water.usgs.gov/automon/

Johnson, V.M., R.C. Tuckfield, M.N. Ridley, R.A. Anderson. 1996. Reducing the sampling frequency of groundwater monitoring wells. Environmental Science and Technology 30, no. 1: 355-358.

Kolpin, D.W., Furlong, E.T., Meyer, M.T., Thurman, E.M., Zaugg, S.D., Barber, L.B., and Buxton, H.T., 2002, Pharmaceuticals, hormones, and other organic wastewater contaminants in U.S. streams, 1999-2000: A National reconnaissance: Environmental Science and Technology, v. 36, no. 6, pages 1202-1211.

Back to:   Robowell Main Page